This means the massive plan comes in about $4.3 billion under the limit.

While it’s likely that the bill was designed to fit inside the window, the test is critical for Republicans because it’s is moving through the Senate via budget reconciliation. Within the recently passed 2018 budget resolution, the Senate attached rules that allow it to pass one bill using the process.

Reconciliation allows a bill to pass with a simple majority vote – and in this case, bypass a Democratic filibuster. Since Republicans control 52 seats in the chamber, this means the bill could pass on a party-line vote.